The present invention relates to a device utilized in braking systems for motor vehicles. More particularly, the present invention has its main application in connection with braking systems for commercial vehicles. Still more particularly, the present invention relates to a method for mounting such a braking system on a motor vehicle.
Larger motor vehicles, e.g. commercial vehicles, are presently designed with lower and lower ground clearances. A primary reason for this is the need to maximize the available cargo space in the vehicle. Since the maximum cargo space is limited by the maximum height allowed and the height of the vehicle chassis, there is consequently a desire to reduce the height of the chassis in order to thereby increase the cargo space. At the same time, maximum ground clearance is desired in order to avoid damage to the vehicle when driving over rough ground. The demands of low height of the chassis and large ground clearance in turn set limitations when designing the braking system of the commercial vehicle. This is particularly true in the case where the braking system comprises a compressed-air driven brake cylinder, which may be mounted standing in a given position in relation to a wheel shaft, and when the brake cylinder comprises a substantially vertically projecting push rod. With such a construction, the height of the chassis of the vehicle is limited by the length of the push rod.
It is known in the prior art that the end of the push rod, which protrudes from the brake cylinder, is normally threaded and connected to a brake key by means of a special lever member.
When the braking system is activated by the driver of the vehicle, the push rod is pressed out from the brake cylinder, thereby influencing the brake key by means of the lever. The brake key, in turn, activates the wheel brake.
With reference to FIG. 1, a previously known system of the above-mentioned kind will be described. FIG. 1 shows a brake cylinder 1, intended to be mounted on a wheel shaft in a commercial vehicle. The brake cylinder 1 comprises a push rod 2, which is pressed out essentially in a vertical direction (i.e., downwards in the drawing) when the braking system is activated by the driver of the vehicle. The movement of the push rod 2 is transferred to a brake key 3 by means of a braking lever 4. The brake key 3 is arranged substantially parallel to the wheel shaft which is to be braked.
When mounting this previously known device, i.e. when the braking lever 4 is to be mounted in order to join the push rod 2 to the brake key 3, the brake cylinder 1 and the brake key 3 have to be pre-installed, i.e. they are placed in the vehicle in advance. In this way, installation of the lever 4 may be accomplished by mounting one end of lever 4, comprising an aperture 5 with internal splines, onto outer splines 6 on the brake key 3. The spline separation which is utilized in this spline coupling will cause the opposite end of the lever 4 to be positioned adjacent to the push rod 2 in a position which may vary within a certain interval in relation to the end of the push rod 4. The exact position for the end of the lever 4 is determined by the fixed spline separation and the length of the lever 4. The splined coupling 5, 6 is thereafter locked by means of a locking screw 7 with appurtenant nut 8.
The next step in the mounting operation is that a link element, consisting of two link members 9 and 10, respectively, is brought together on both sides of the push rod 2 and the end of the lever 4, which has been placed adjacent to the push rod 2. The first link member 9 is joined to the second link member 10 by means of two screws, 11 and 12, which are inserted into corresponding holes, 13 and 14, in the second link member 10, while a pin 15 in the first link member 9 is passed through a hole 16 in the lever 4 and into a further hole 17 in the second link member 10. Thereafter, the link element 9, 10 is screwed on by means of the screws, 11 and 12, and nuts, 18 and 19. The link members, 9 and 10, further comprise internal threads 20 (which are only evident from the link member 10 in FIG. 1) which interact with threads 21 on the push rod 2. In this way, the push rod 2 may be locked to the link elements 9, 10 and transfer its movement to the brake key 3 by means of the lever 4.
As mentioned above, the spline separation of the splined coupling 5, 6 implies that the end portion of the lever 4 facing towards the push rod 2 will be positioned in a position which may vary vertically within a certain interval. This interval is normally of the magnitude of approx. 30 mm. Thus, the length of the link element 9, 10 cannot be below this interval, since it has to be utilized for bridging the distance between the push rod 2 and the lever 4. The fact that the interval must be accomodated by the link element 9, 10, in its turn, means that this has to project downwards a relatively long distance below the push rod 2. This constitutes a disadvantage, since it creates an essential limitation when the ground clearance and the height of the chassis of the vehicles are concerned.
A main object of the present invention is to achieve an improved device for joining a push rod and a brake key in a braking system, particularly for commercial vehicles, which braking system utilizes a compressed-air driven brake cylinder with a vertically projecting push rod. In particular, it is an object of the present invention to create conditions for optimizing the relation between the ground clearance and the height of the chassis of the vehicle.
A further object of the invention is to provide a simplified mounting of a braking system for a commercial vehicle, having a minimum number of components and working steps in the mounting operation.
In accordance with the present invention, these and other objects have now been realized by the invention of brake system for use in motor vehicles comprising a brake cylinder including a push rod having an end portion projecting from the brake cylinder upon activation of the brake cylinder, a brake key for activating a wheel brake on the motor vehicle, a braking lever including a first end and a second end, the first end of the braking lever adapted for connection to the brake key and the second end of the braking lever adapted for connection to the push rod, and a mounting member affixed to the push rod at a location between the brake cylinder and the end of the push rod, the mounting member including a first attachment member and the braking lever including a second attachment member whereby the braking lever can be coupled to the push rod at a location between the brake cylinder and the end of the push rod by attaching the first and second attachment members to each other. In accordance with one embodiment of the brake system of the present invention, the first attachment member comprises a predetermined shape of the mounting member and the second attachment member comprises a predetermined complementary shape of the braking lever. In a preferred embodiment, the predetermined shape of the mounting member comprises a pin and the predetermined complementary shape of the braking lever comprises an aperture.
In accordance with one embodiment of the brake system of the present invention, the push rod includes external threads and the mounting member comprises a substantially sleeve-shaped member including internal threads adapted to mate with the external threads of the push rod.
In accordance with another embodiment of the brake system of the present invention, the system includes a support including a first end and a second end, the first end of the support adapted for connection to the mounting member and the second end of the support adapted for connection to the braking lever. In a preferred embodiment, the mounting member includes a third attachment member and the first end of the support includes a fourth attachment member. More preferably, the third attachment member comprises a predetermined shape of the mounting member and the fourth attachment member comprises a predetermined complementary shape of the support. Most preferably, the predetermined shape of the mounting member comprises a pin and the predetermined complementary shape of the support comprises an aperture.
In accordance with another embodiment of the brake system of the present invention, the first end of the braking lever is adapted for connection to the brake key by means of a splined coupling.
In accordance with the method of the present invention, a method has been developed for mounting a brake system in a motor vehicle, the brake system comprising a brake cylinder including a push rod having an end portion projecting from the brake cylinder upon activation of the brake cylinder and a brake key for activating a wheel brake on the motor vehicle, the method comprising mounting a mounting member on the push rod at a location between the brake cylinder and the end of the push rod, providing a braking lever having a first end and a second end, connecting the second end of the braking lever to the mounting member at the location between the brake cylinder and the end of the push rod, and connecting the second end of the braking lever to the brake key in a direction substantially parallel to the longitudinal direction of the brake key. In a preferred embodiment, the mounting member includes a first attachment member having a predetermined shape integral therewith and the second end of the braking lever includes a second attachment member having a predetermined complementary shape integral therewith, the method further comprising connecting the second end of the braking lever to the mounting member by guiding the predetermined shape of the mounting member into the predetermined complementary shape of the second end of the braking lever.
In accordance with one embodiment of the method of the present invention, the method includes separately connecting the mounting member to the braking lever by means of a separate support.
The present invention is based on a mounting device which, together with the braking lever, comprises means for coupling the push rod to the braking lever, by means of the mounting device, at a point which is situated within the end of the push rod which projects from the brake cylinder. In this way, the only limitation for the height of the chassis/ground clearance is given by the length of the push rod, i.e. the distance between the brake cylinder and the lever may be made shorter than in previously known devices.
According to a preferred embodiment of the present invention, the push rod may be coupled to the lever by means of the mounting device since the mounting device comprises a modification of shape, preferably in the form of a pin, which interacts with a corresponding modification of shape, preferably a hole, which has been provided in the braking lever.